1. Field of Invention
This invention relates to semiconductor device packages, and more particularly to bonding techniques used to connect integrated circuit input/output (I/O) pads to bond traces of semiconductor device packages.
2. Description of Related Art
During manufacture of an integrated circuit (e.g., a microprocessor), signal lines formed upon the silicon substrate and to be connected to external devices are terminated at flat metal contact regions called input/output (I/O) pads. Following manufacture, the integrated circuit is typically secured within a protective semiconductor device package. Each I/O pad of the chip is then connected to a bonding pad of the device package, and ultimately to a terminal which typically extends from the periphery of the package.
As integrated circuit fabrication technology improves, manufacturers are able to integrate more and more functions onto single silicon substrates. As the number of functions on a single chip increases, however, the number of signal lines which need to be connected to external devices also increases. The corresponding numbers of required I/O pads and device package terminals increase as well, as do the complexities and costs of the device packages.
Common methods used to connect the I/O pads of the integrated circuit to bond traces of the device package include wire bonding and tape automated bonding (TAB). In wire bonding, connections are made using fine metal wires (e.g., gold or aluminum wires). FIG. 1a is a partial perspective view of an integrated circuit 10 attached to an upper surface of a substrate 12 of a semiconductor device package. I/O pads 14 of integrated circuit 10 are arranged at or near the perimeter of integrated circuit 10, wherein I/O pads 14 are placed in close lateral proximity to bond traces 16 (often referred to as bonding "fingers"). Bonding wires 18 extend and make electrical connection between I/O pads 14 and bond traces 16. Bonding traces 16 are connected to terminals of the device package by electrically conductive signal traces.
TAB techniques connect I/O pads of the integrated circuit to bond traces of the device package using fine-line conductors etched from one or more sheets of metal (e.g., copper). The electrically conductive sheet is bonded to a sheet of a dielectric material (e.g., polyimide film), then portions of the conductive sheet are selectively removed in order to form the TAB conductors. The sheet of dielectric material maintains proper conductor spacing. FIG. 1b is a partial perspective view of integrated circuit 10 having I/O pads 14 bonded to etched metal "beam" conductors 20 of a flexible TAB "tape" 22. Conductors 20 are bonded to a sheet of dielectric material 23 and connected to terminals of the device package.
In wire bonding, each bonding wire is typically installed one after another in sequence. In TAB, on the other hand, multiple connections are made at the same time (i.e., in parallel). Thus wire bonding is a relatively slow process compared to TAB. In wire bonding, two or more bonding wires may inadvertently touch one another, causing an electrical short circuit and improper operation of the packaged semiconductor device. TAB tapes prevent conductors from coming into contact with one another. TAB tapes are, however, more expensive than bonding wire. However, the TAB tapes may also function as semiconductor device packages. Thus wire bonding and TAB techniques have benefits and drawbacks.
It would be advantageous to combine wire bonding and TAB techniques to form a hybrid bonding technique which includes the advantages of both methods. For example, the current states of wire bonding and TAB technologies place lower limits on the minimum distances between I/O pads of integrated circuits (i.e., I/O pad "pitch"). By combining the two technologies, however, it is possible to increase the number of I/O pads per unit of integrated circuit surface area (i.e., I/O pad density). Increasing I/O pad density not only helps solve the increasing I/O pad problem, but also allows the dimensions of semiconductor device packages employing the hybrid approach to be reduced. Such size reductions are advantageous, especially in portable applications.